v0.3.0

This is a compatibility release, it addresses a theoretical Namespace Conflict with https://github.com/matsumoto-r/mruby-redis.

If you used the macros defined in https://github.com/Asmod4n/mruby-hiredis/blob/master/include/mruby/hiredis.h you need to adjust your app.